Trump deleted the tweet and reposted it to the proper Lee Greenwood within an hour:

But it was too late. Twitter had the receipts for both Trump and Fox News:

Trump thanked Singer Lee Greenwood (God Bless The USA) today on Twitter, except it was the wrong "Lee Greenwood" The "Lee Greenwood" he actually thanked is an attorney who marched in the Anti-Muslim Ban Parade. Mr Trump is intelligent and is a graduate of the Ivy League. pic.twitter.com/OAQ3ggAjBH